Scientists from the US, China, and Scotland have determined that the earliest herbivore marine reptile was a crocodile-sized animal named Atopodentatus unicus. The Atopodentatus unicus, the bizarre reptile that roamed the Earth 242 million years ago in southern China, had a jaw shaped like a hammerhead, peg-like teeth along the jaw’s edge and needle-like teeth inside its mouth.

The reptile’s poorly-preserved fossil was discovered in 2014. Initially, scientists thought that its beak resembled that of a flamingo but now, they found that this was not a beak but a portion of its hammerhead-shaped jaw, which the animal used to chew on plants on the sea floor. The findings have been published on May 6 in the journal Science Advances.

The research team believes that its front peg-like teeth were used to scrape the sea plants off of the rocks. The Atopodentatus unicus then sucked this food and used its needle-like teeth to trap the plants while letting the water leak out, kind of like a sieve. The same filter-feeding technique can be observed in how whales use their baleen. The Atopodentatus is eight million years older than other animals with the same feeding system, the team notes.


A fossil of Atopodenatus unicus is alongside a reconstruction showing what it would have looked like in life. Credit: Nick Fraser

“To figure out how the jaw fit together and how the animal actually fed, we bought some children’s clay, kind of like Play-Doh, and rebuilt it with toothpicks to represent the teeth,” explains co-author Olivier Rieppel, Rowe Family Curator of Evolutionary Biology at The Field Museum in Chicago. “We looked at how the upper and lower jaw locked together, and that’s how we proceeded and described it.”


To determine the way that Atopodenatus unicus’ jaw worked, the scientists made models out of children’s clay and toothpicks. Credit: Olivier Rieppel, The Field Museum

Moreover, the Atopodentatus’ discovery sheds light into the largest mass extinction 252 million years ago. It supports other studies that asserted some animals recovered and thrived faster than previously believed.

“Animals living the years surrounding the Permian-Triassic extinction help us see how life on earth reacted to that event,” adds Rieppel. “The existence of specialised animals like Atopodentatus unicus shows us that life recovered and diversified more quickly than previously thought. And it’s definitely a reptile that no one would have thought to exist–look at it, it’s crazy!”